Yes, fore/aft refers to moving the saddle forward or back. You might play around with it as there's no one right rule of thumb to follow. Most instructors will tell you that your knee should be above the pedal spindle when your foot is in the 3 o'clock position. But that's a general rule. I need to be farther back than that.
That said, you likely nee to dial down the resistance. You should strive to maintain proper form first and foremost. As for getting your heartrate up, you should be able to do that by increasing your cadence using a pedal resistance that doesn't overly tax your knees. Frankly,those drills get my heart rate higher than climbing drills.
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